Area controlled, thrust vectoring vane cascade with nutating control vane

ABSTRACT

A plurality of cascade vanes (28, 29, 30) for directing a flow of gas (20) is provided with at least one flow regulating vane (36) which counterrotates with respect to the cascade vanes (28, 29, 30) over a gas flow vectoring range of motion. The cascade vanes (28, 29, 30) and flow regulating vane (36) corotate when moving through an adjacent stowing range of motion for achieving a stowed, gas flow blocking arangement.

This invention was made with Government support under a contract awardedby the Department of the Air Force. The Government has certain rights inthis invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

Attention is hereby directed to copending commonly assigned U.S. patentapplications Ser. No. 053,288 "Area Controlled, Thrust Vectoring VaneCascade", Harold G. Guerty, and "Linkage for Area Controlled, ThrustVectoring Vane Cascade", Eric J. Ward, Philip R. Scott and Edward B.Thayer, filed on even date herewith and which disclose related subjectmatter.

TECHNICAL FIELD

This invention relates to a vane cascade having a plurality of variableposition, pivoting vanes for directing a flow of gas.

BACKGROUND

The use of a cascade of individually pivotable vanes for selectablydiverting a flow of gas passing therethrough is a known method forachieving a desired thrust direction in an aircraft or other similarapplication. Such systems may be used to provide additional lift duringcertain flight maneuvers, or to reverse the normal direction of thrustfrom a gas turbine engine or the like in order to decelerate theaircraft during landing or at other times.

One such variable position vane cascade is shown in U.S. Pat. No.3,100,377 issued to R. E. Kosin et al. The outlet of a gas turbineengine is provided with a plurality of individual movable vanes fordirecting the engine exhaust either rearwardly along the main axis ofthe aircraft during normal forward flight, or downwardly, transverse tothe major aircraft axis for providing additional upward lift duringvertical or short takeoff or landing maneuvers. The vanes traverse arange of motion between these two positions, thus providing a pluralityof intermediate thrust vectors for transitioning between these twoflight modes.

U.S. Pat. No. 3,335,960 issued to E. D. Alderson shows a gas turbineengine outlet equipped with a plurality of movable vanes for providingboth thrust vectoring and thrust control by spoiling the gas flow streamin order to reduce thrust. While known in the prior art, such variableposition vane cascades typically utilize a plurality of actuators foraligning each vane according to an individual schedule or other controlsignal to provide the desired collective thrust vector and/or gas outletflow area.

In particular, for vane cascades wherein it is desired to provide thrustvectoring for a flow of exhaust gas from a gas turbine engine or thelike, it is desirable that the collective exhaust gas flow area throughthe cascade be held nearly constant in order to avoid inducinginstability in the operation of the gas turbine engine. As will beappreciated by those skilled in the operation of gas turbine engines, arapid increase or decrease in the area of the engine exhaust nozzle canlead to engine rotor overspeed or compressor blade stalling,respectively.

For vane cascades having a plurality of vanes pivoting in unison forvectoring thrust, it will be appreciated that the nozzle outlet areameasured normal to the flow of gas from the vectoring cascade will be afunction of the sine of the vane angle. Thus, the outlet area of thecascade having vanes positioned at a 45° angle with respect to thegeneral cascade plane will be approximately 70% of the flow area withthe vanes oriented normally, i.e. 90°, with respect to the cascadeplane.

This nearly 30% variation in gas flow area can occur in applicationswherein a variable vane cascade is provided for discharging a flow ofexhaust gas from a thrust-reversing and/or thrust-maneuvering gasturbine engine exhaust nozzle. In such applications it is desirable toorient the plane of the cascade transversely with respect to theaircraft major axis, pivoting the individual vanes in unison to directthe flow of exhaust gases rearwardly for achieving a forward thrustflight mode, laterally for achieving high transverse and no axialthrust, and forwardly for achieving a rearward or reversing thrust. Aswill be appreciated by those familiar with such thrust vectoring needsand applications, the time of transition between any two thrust modesmay be on the order of 1-2 seconds, especially during landing or highspeed evasion maneuvers.

As with any aircraft application, the requirement for reduced weight andcomplexity is a high priority goal for designers in this field. Multipleactuator arrangements, while providing high flexibility in positioningindividual vanes, are relatively heavy and complex to operate. What isrequired is a simple, single actuator, variable position vane cascadewhich simultaneously vectors the flow of gas therethrough whilemaintaining a constant collective gas flow area.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide avectoring vane cascade for selectably discharging a flow of gas turbineengine exhaust, or the like.

It is further an object of the present invention to provide a vanecascade which achieves a constant collective gas flow area over therange of vane motion corresponding to the thrust vectoring operation ofthe vane cascade.

It is further an object of the present invention to achieve suchconstant flow area by coordinating the movement of at least one flowregulating vane in an opposite direction of that of the cascade vanes,at least within the vectoring range of motion.

It is further an object of the present invention to provide a cascadeand flow regulating vane arrangement wherein the flow regulating andcascade vanes are selectably pivotable into an overlapping arrangementfor establishing a flow barrier to any gas flow therethrough.

It is still further an object of the present invention to provide alinkage for accomplishing such vane movement with only a single linearactuator.

According to the present invention, a thrust vectoring gas dischargevane cascade is provided with a plurality of spanwisely parallelpivoting vanes, movable in unison for selectably directing a flow ofgas, such as the exhaust gas of a gas turbine engine, therefrom. Thecascade vanes move between a plurality of flow directing positions,including a first forward thrust position in which the vanes are pitchedfor directing the exhausted gas rearwardly, a second, lateral thrustposition in which the vanes are oriented normal to the general plane ofthe cascade structure for exhausting gas directly from the cascade, anda third, rearward thrust position in which the vanes are pitched fordirecting the exhausted gas forwardly.

The present invention further provides means for avoiding substantialvariation in the collective cascade gas flow area as the vanes move overthe flow directing, or thrust vectoring, range of motion. According tothe present invention, a flow regulating vane is provided adjacent oneof the end vanes of the cascade. The flow regulating vane is pivotableabout an axis parallel to the pivot axes of the cascade vanes and isrotated contrary to the movement of the cascade vanes between the first,second, and third positions.

In operation, the flow regulating vane is chordwisely aligned with thecascade vanes when the cascade vanes are in the first and thirdpositions, thereby cooperably exhausting gas from the cascade forwardlyor rearwardly as desired. When the cascade vanes move into the second,normal position, an opposite rotational movement of the flow regulatingvane results in a blocking orientation wherein the flow regulating vaneis chordally perpendicular with the adjacent end cascade vane, therebyblocking off a portion of the gas flow and holding the collectivecascade gas flow area constant.

A further embodiment of the present invention includes means forreversing the direction of rotation of the flow regulating vane as thecascade vanes move from one of the pitched, thrust vectoring positionsinto an overlapping, stowed position wherein each vane overlaps orotherwise contacts the next adjacent vane. The overlapped, stowed vanesprovide a closed gas barrier for aerodynamic or flow blocking purposes.

The flow regulating vane, rotating now in unison with the cascade vanesas they move over a stowing range of motion defined between the firstpitched position and the stowed, overlapping position, also achieves anoverlapping orientation with respect to the adjacent end vane. Thisreversing pivoting motion of the flow regulating vane, also termed"nutation", provides a stowable, constant area vane cascade which iseffective and efficient in providing selectable thrust vectoring in avariety of applications.

A further embodiment of the present invention provides a vane cascadewith both first and second flow regulating vanes. Each flow regulatingvane is positioned adjacent one or the other of the end vanes of thecascade. The flow regulating vanes pivot in conjunction with each otherand oppositely with respect to the cascade vanes over the thrustvectoring range of motion, and, in the stowable embodiment, inconjunction with the cascade vanes over the stowing range of motion. Byproviding dual flow regulating vanes, the present invention allowsgreater flexibility in the arrangement and sizing of the cascade, aswell as maintaining a generally constant thrust centerline duringvectoring operation.

Another feature of the cascade according to the present invention is alinkage for orienting the individual blades by means of a single linearactuator. This linkage, by avoiding the multiple actuators common in theprior art, allows reduced weight and complexity, desirable features inaircraft as well as other applications.

More particularly, the linkage according to the present inventionprovides a single unison link driven by a linear actuator forpositioning the cascade vanes in unison as set forth above. A cam race,secured to the unison link, drives a second linkage for imparting theappropriate nutational motion to the flow regulating vane or vanes inresponse to the translation of the unison link, thereby ensuring properorientation of the flow regulating vane or vanes at every point withinthe cascade operating ranges of motion.

Both these and other objects and advantages of the cascade arrangementaccording to the present invention will be apparent following a reviewof the following description and the appended claims and drawingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b show an axial cross section of a gas turbine engineexhaust nozzle including a vectoring vane cascade.

FIGS. 2a, 2b, and 2c show a schematic view of a vane cascade accordingto the present invention operating over a vectoring range of motion.

FIGS. 3a, 3b, 3c, and 3d show a cross-sectional view of a stowablevectoring vane cascade according to the present invention, including adrive linkage therefor.

FIGS. 4a, 4b, and 4c show a stowable vectoring vane cascade with analternative linkage therefor.

FIG. 5 shows a cross-sectional view of a vectoring vane cascade havingdouble flow regulating vanes according to the present invention. A thirdembodiment of the linkage according to the present invention is alsodisclosed therein.

FIG. 6 shows a graphical representation of the variation of exhaust gasflow area of a vectoring vane cascade both for a simple unison cascadearrangement and for the flow controlled arrangement according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTIVE METHOD AND STRUCTURE

FIG. 1a shows a cross-sectional view of an exhaust nozzle 10 takenthrough the central axis 12 of the gas turbine engine (not shown) andthe nozzle 10. The nozzle is of 2D configuration, having a pair ofspaced-apart sidewalls 14 and movable upper and lower flap assemblies16, 18 extending therebetween. Such nozzles typically discharge theexhaust gas 20 from the gas turbine engine rearwardly for providingforward thrust for driving an aircraft or the like.

Occasionally it is desired to provide reverse or other direction thrustfor the purpose of maneuverability or for arresting velocity duringlanding of the aircraft. The nozzle as shown in FIGS. 1a and 1b mayprovide such alternative thrusting capability as shown in FIG. 1bwherein the forward flaps 22, 24 of the flap assemblies 16, 18 pivotinto a blocking relationship with respect to the axial exhaust flow pathdefined as in FIG. 1a.

Exhaust gases 20 thus are diverted laterally as shown in FIG. 1b,passing out of the nozzle 10 through opposed vane cascades 26. As willbe described in more detail hereinbelow, the opposed cascades 26 containa plurality of movable vanes for selectably directing the flow ofexhaust gases 20. Such a nozzle as shown in FIGS. 1a and 1b is disclosedand described in greater detail, although without the vane cascades 26according to the present invention, in U.S. Pat. No. 4,641,782 issued toWoodward.

FIRST EMBODIMENT

FIGS. 2a and 2b show an individual vane cascade 26 according to thepresent invention. Exhaust gases 20, possibly diverted from the axialgas flow path as shown in FIGS. 1a and 1b, flow into the vane cascade 26from above as shown. The vane cascade 26 includes a plurality of cascadevanes 28, 29, 30, each pivotable about a corresponding axis 31, 32, 33,extending spanwisely through the respective vane 28, 29, 30. FIG. 2ashows the cascade vanes 28, 29, 30 in a first, forward thrust positionwherein the vanes 28, 29, 30 are pitched rearwardly for diverting theexhaust gas 20 for producing thrust in the opposite, or forwarddirection. A static structure 34 surrounds and supports the cascade 26by any of a number of means, such as bearings at the vane span ends,well known in the art and not discussed further herein.

According to the present invention, the vane cascade 26 is provided witha flow regulating vane 36 disposed adjacent to one of the cascade endvanes 30 and pivotable about a spanwisely extending axis 37 which isparallel to the axes 31, 32, 33 of the cascade vanes 28, 29, 30. Asshown in FIG. 2a and in subsequent FIGS. 2b and 2c, cascade vanes 28, 9,30 are pivotable 38 in unison about their respective pivot axes 31, 32,33 for selectably directing the exhaust gas 20 laterally as shown inFIG. 2b, or forwardly as shown in FIG. 2c, as well as a variety of otherdirections therebetween. For purposes of reference hereinafter thelateral discharge as shown in FIG. 2b is termed "a second position"wherein the cascade vanes 28, 29, 30 are oriented generally normal tothe plane 40 of the cascade defined by the cascade vane axes 31, 32, 33.Such second position vanes, by directing the exhaust gas laterally withrespect to the cascade 26, produce a high lateral thrust without asignificant axial component.

As discussed in the Background section hereinabove, the gas flow areadefined by a plurality of vanes pivotable in unison is a function of thesine of the angle 42 formed between the chordal lines 44 of the vanes28, 29, 30 and the plane 40 of the vane cascade. The undesirablevariation in area as the cascade vane angle varies over a vectoringrange of motion defined by the first, 45° position of FIG. 2a, thesecond 90° position of FIG. 2b and the third 135° position of FIG. 2a iscontrolled by the opposite rotation 46 of the first flow regulating vane36 as shown in FIGS. 2a-c. Thus, in FIG. 2a, the flow regulating vane 36is oriented chordally parallel to the adjacent end vane 30, fordirecting the exhaust gases 20 rearwardly in parallel with the cascadevanes 28, 29, 30.

As is shown in FIG. 2b, the flow regulating vane 36 has rotated so as tobe chordally perpendicular with respect to the adjacent end vane 30,blocking off a portion of the cascade 26 thus helping to maintain thegas flow area therethrough.

As will further be apparent from examining FIGS. 2b and 2c, the flowregulating vane 36 has continued to pivot oppositely with respect to thecascade vanes 28, 29, 30, thus again becoming chordally parallel theretoand contributing to directing the exhaust gas 20 in the forwarddirection for generating rearward or reversing thrust.

The flow regulating vane 36, by rotating oppositely with respect to theunison cascade vanes, 28, 29, 30 as they move in the gas thrustvectoring range of motion defined by FIGS. 2a-2c, maintains a nearlyconstant collective gas flow area therethrough, avoiding undesirable andpossibly destabilizing exhaust area variations. Unlike prior art vanemanipulation systems and methods, the counter-rotating flow control vane36 according to the present invention is a simple,geometrically-determined area regulating means which does not depend onpredetermined scheduling of individual vanes to ensure the propercollective gas flow area. A variety of linkages or other actuating meansmay be used to position the vanes 28, 29, 30, according to the methodshown schematically in FIGS. 2a-2c. Several of such linkages aredescribed hereinbelow.

As will be apparent from examining the motion of the vanes 28, 29, 30,36 over the vectoring range of motion shown in FIGS. 2a-2c, when thecascade vanes 28, 29, 30 are moved into a stowed, or a flow-blockingrelationship wherein each adjacent vane overlaps the next adjacent vanefor forming an unbroken barrier against gas flow, the flow regulatingvane 36, if it continues to rotate in the opposite direction withrespect to the cascade vanes 28, 29, 30 will be oriented perpendicularto the plane 40 of the cascade 26. While such may not be a problem for acascade 26 which is always passing a flow of gas 20 therethrough and istherefore never stowed, for certain applications, such as the vectoringnozzle 10 shown in FIGS. 1a and 1b, it is desirable to stow all suchvanes in an overlapping, gas blocking relationship.

SECOND EMBODIMENT

This is accomplished according to the present invention by extending therange of movement of the flow regulating vane 36 to include a nutationalrotation, reversing its relative rotation with respect to the cascadevanes 28, 29, 30 as the cascade vanes move from the first position intoa stowed position as shown in FIG. 3a. The co-rotation of the flowregulating vane 36 in response to movement of the cascade vanes 28, 29,30 in a stowing range of motion defined between the stowed position asshown in FIG. 3a and the first thrust vectoring position as shown inFIG. 3b allows the vane cascade 26 to open smoothly between a stowed,blocking mode wherein little or no gas flow 20 may pass therethrough,into the forward thrust mode wherein the gas 20 is diverted rearwardlyby the pitched vanes 28, 29, 30, 36 as shown.

The reverse pivoting motion of the flow regulating flap 36 over thevectoring range of motion is shown in FIGS. 3b, 3c, and 3d whichparallel FIGS. 2a, 2b, 2c discussed hereinabove. Such motion providesthe same area controlling function as achieved by the simpler, purelycounter-rotating vane system described above, but allows the achievementof the overlapping stowed position of FIG. 3a for aerodynamic, flowregulating, or other purposes.

FIGS. 3a-3d also disclose a linkage 46 for orienting both the cascadevanes 28, 29, 30 and the first flow regulating vane 36 in response to asingle linear motion 48. This is accomplished through an elongatedunison link 50 extending across the cascade 26 and being connected at aplurality of spaced-apart locations to each individual cascade vane 28,29, 30 by a corresponding vane drag link 52.

The first flow regulating vane 36 is driven in a reversing, pivotingmotion as required in this first embodiment linkage 46 by a first curvedcam race 54 secured to the unison link 50 and movable therewith, and asecond, static cam race 56 disposed in the surrounding static structure34. A cam roller 60 rides in both races 54, 56, being driven in atransverse reciprocating motion with respect to the elongated unisonlink 50. The roller 60 drives a flow regulating vane link 62, drives thefirst flow regulating vane 36 directly via a pivot connection therewith.

As will be appreciated by those skilled in the art, this simple strokingmotion of the first embodiment linkage 46 produces both the multi-vaneunison motion for the cascade vanes 28, 29, 30, and the nutatingmovement of the first flow regulating vane 36, including corotation ofthe first flow regulating vane 36 as the cascade vanes 28, 29, 30 rotatethrough the stowing range of motion defined between the positions ofFIGS. 3a and 3b, and the counter-rotating motion of the first flowregulating vane 36 as the cascade vanes 28, 29, 30 move through thethrust vectoring range of motion defined between the positions shown inFIGS. 3b, 3c, 3d.

THIRD EMBODIMENT

FIG. 4a shows a more detailed view of a further embodiment of a variableposition vane cascade 26 according to the present invention. Cascadevanes 27, 28, 29, 30 pivot in unison about respective pivot axes 35, 31,32, 33 responsive to the linear movement 48 of a unison link 50. Theunison link 50 is driven by a linear actuator 59 secured between aportion of the link 50 and the static structure 34.

As in the second embodiment discussed hereinabove, a cam race 54 issecured to the unison link 50 and translates therewith. A cam roller 60is received within the race 54 and is further pivotally secured to thestatic structure 34 by an idler link 64 which restrains the roller 60against axial movement thereby resulting in a reciprocating motiontransverse to the movement of the unison link 50 as the link 50 isstroked 48.

The transverse motion of the roller 60 imparts nutational motion to theflow regulating vane 36 via a linkage comprising the first flowregulating vane drive link 66 and a corresponding crank 68 pivotallysecured to the roller 60 and to each other 70. By using a four barlinkage 64, 66, 68, 34 driven by the roller 60 and cam race 54, theapparatus, and especially the linkage thereof, according to the presentinvention provides a simple, powerful mechanism for orienting the vanes27, 28, 29, 30, 36 as the cascade 26 is operated over both stowing andthrust vectoring ranges of motion.

In particular, the four bar linkage 64, 66, 68, 34 for driving the firstflow regulating vane 36 may be modified by reconfiguring the cam race54, or resizing the individual links 64, 66, 68, thereof to permitrescheduling or otherwise modifying the motion of the first flowregulating vane 36 in response to the engine nozzle outlet arearequirement, thrust vectoring direction, or other parameters which maybe influenced by the relative orientation of the first flow regulatingvane 36 during operation of the cascade 26.

FIGS. 4a, 4b, and 4c depict the orientation of the individual vanes 27,28, 29, 30, 36 of the cascade 26 at the first, second, and thirdpositions which define the thrust vectoring range of motion. FIG. 4ashows the individual vanes pitched rearwardly for generating forwardthrust by the discharged exhaust gas 20. As noted above, the firstforward thrust position shown in FIG. 4a has been achieved by thecorotation of the cascade vanes 7, 28, 29, 30 and the first flowregulating vane 36 in response to linear translation of the unison link50 and the interaction of the cam roller 60 and the associated linkage64, 66, 68. Cam roller 60 as shown in FIG. 4a has thus reached the topportion of the curved cam race 54 and will therefore begin to reversethe displacement of the cam roller 60 as well as the direction ofrotation of the first flow regulating vane 36 upon further movement ofthe unison link 50 in the rearward or righthand direction.

FIG. 4b shows the cascade vanes 27-30 in the second or lateral thrustvectoring position, wherein the cascade vanes of FIG. 4b have rotated 38into a substantially normal orientation with respect to the cascadeplane 40 and wherein the counter-rotation 46 of the first flowregulating vane 36 as induced by the reverse transverse displacement ofthe cam roller 60 has caused the first flow regulating vane 36 to moveinto a blocking orientation thereby reducing the collective cascade gasflow area.

FIG. 4c shows the vanes 27-30, 36 in the third, reverse thrust positionwherein the first flow regulating vane 36 has moved into a chordallyparallel orientation with respect to the adjacent cascade vane 30 fordirecting the exhausted gas 20 in a forward direction.

FOURTH EMBODIMENT

FIG. 5 shows still a further embodiment of the cascade assembly 26according to the present invention, wherein two flow regulating vanes36, 70 are provided for controlling the gas flow area of the cascade 26over the vectoring range of motion thereof. As with the previousembodiments, a plurality of cascade vanes 28, 29, 30 rotate in unisonunder the influence of a unison link 50 driven by a linear actuator 59shown displaced from its normal position for clarity. A cam race 54 issecured to the unison link 50 and reciprocates therewith for causingreversing transverse movement of the cam roller 60 as in the previousembodiments.

In this embodiment, the roller 60 drives a toggle link 72 pivotallysecured 74 to the static structure 34 for driving the first flowregulating vane crank 68 via the first flow regulating vane drive link66. The toggle link and crank arrangement 72, 66, 68 provides a morecompact linkage over either the four bar linkage 64, 66, 68, 34 of thethird embodiment, or the double cam arrangement of the second embodimentdiscussed hereinabove.

As the movements of the individual vanes 28, 29, 30, 36 have been welldiscussed hereinabove and are essentially similar in this equivalent,but distinct, embodiment, discussion herein shall be confined to onlythe additional linkage and movement induced in the second flowregulating vane 70 which extends spanwisely parallel with the other endvane 28 of the plurality of cascade vanes 30, 29, 28 and adjacentthereto.

The second flow regulating vane 70 rotates in unison with the first flowregulating vane 36 under the influence of the push rod 76 extendingtherebetween. First and second push rod cranks 78, 80 are secured to therespective regulating vanes 36, 70 for manipulating the second vane 70in response to the rotation of the first vane 36.

The dual flow regulating vane arrangement of this fourth embodimentprovides further flexibility to the cascade designer by permitting agreater portion of the available cascade flow area to be opened orclosed as the cascade vanes 30, 29, 28 are positioned for directing theexhaust gas 20 over the vectoring range of motion. Such flexibility isuseful in larger cascade arrangements wherein a single regulating vanemay not provide adequate blocking or other area control capacity forreducing the undesirable gas flow area variation discussed above. Itshould be noted that the double vane concept of this embodiment isequally applicable to the preceding embodiments wherein it would beoperable to achieve the enhanced flexibility and area control advantagesdiscussed above.

FIG. 6 provides a graphical representation of the variation of the gasflow area of a cascade arrangement 82 according to the present inventionand a prior art cascade arrangement 84 wherein the individual vanespivot in unison for selectably directing a flow of gas therethrough.FIG. 6 shows the variation of the ratio of actual cascade flow area,A_(F), to the maximum achievable cascade flow area A_(MAX). For theprior art, uncontrolled vane cascade, the curve 84 shows a maximum arearatio occurring at the normal, or 90° orientation of the vanes withrespect to the cascade plane 40. As noted in the Background sectionabove, the area is a function of the sine of the vane angle, falling offon each side of the 90° maximum as the vanes pitch to one side or theother.

Curve 82 shows the beneficial results of using one or more flowregulating vanes according to the present invention. At the 45° and 135°locations, i.e., the first and third thrust vectoring positions, thearea ratios are identical to that of the prior art system 84. As thecascade vanes are rotated into the lateral thrust, 90° orientation,i.e., the second position, the flow regulating vane or vanes have movedto block off a portion of the cascade gas flow area, thus maintainingthe collective cascade area approximately constant over the criticalrange of motion.

The cascade arrangement according to the present invention has thus beendisclosed in four equivalent embodiments well adapted for achieving theobjects and advantages set forth hereinabove. It will be appreciated bythose skilled in the art that such objects and advantages may also beachieved by further, essentially equivalent, embodiments thereof;therefore the above-mentioned structures should not be considered in alimiting sense, but rather as being simply illustrative of the preferredand alternative embodiments of the invention.

We claim:
 1. An exhaust gas thrust vectoring vane cascade having aplurality of individual cascade vanes pivotable in unison about acorresponding plurality of parallel pivot axes, the cascade vanes beingpivotable over a thrust vectoring range of motion, includinga firstforward thrust position, wherein the cascade vanes are pitched fordischarging the exhaust gas rearwardly, a second, lateral thrustposition, wherein the cascade discharges the exhaust gas normally withrespect to the cascade, and a third, rearward thrust position, whereinthe cascade vanes are pitched for discharging the exhaust gas forwardly;the cascade vanes further being pivotable over an adjacent stowing rangeof motion defined between the first forward thrust position and a stowedposition wherein each vane in the cascade contacts each adjacent vanethereto in an overlapping relationship, the stowed adjacent vanescollectively blocking off the cascade gas flow; means for providing aconstant collective gas flow area through the vane cascade over thethrust vectoring range of motion, comprising: a first flow regulatingvane disposed adjacent one end vane of the plurality of cascade vanesand pivotable about an axis parallel to the pivot axes thereof, meansfor pivoting the first flow regulating vane responsive to the pivotingof the cascade vanes, wherein, the first flow regulating vane pivotscounter-rotationally with respect to the cascade vanes over the thrustvectoring range of motion, such that the first flow regulating vane isoriented chordally parallel to the one end vane when the cascade vanesare in the first and third thrust vectoring positions, and the firstflow regulating vane is oriented substantially perpendicular to the oneend vane when the cascade vanes are in the second, lateral thrustposition, and wherein the first flow regulating vane pivotsco-directionally with the cascade vanes over the stowing range of motionbetween the first and stowed positions, such that the first flowregulating vane achieves an overlapping relationship with the adjacentone end vane when the cascade vanes are in the stowed position.
 2. Thevane cascade as recited in claim 1 further comprising:a second flowregulating vane, disposed adjacent an other end vane of the vane cascadeand pivotable about an axis parallel thereto, and means for pivoting thesecond flow regulating vane in unison with the first flow regulatingvane over the vectoring and stowing ranges of motion.
 3. A method forachieving a constant collective gas flow area through a cascade having aplurality of adjacent individual vanes each pivotable in unison about acorresponding plurality of parallel pivot axes, the cascade vanes beingpivotable over a vectoring range of motion including a first pitchedorientation, a second orientation normal to the cascade, and a thirdpitched orientation opposite to the first orientation, and further beingpivotable over a stowing range of motion defined between the firstpitched orientation and a stowed orientation wherein each adjacent vaneis disposed in an overlapping relationship for closing off the flow ofany exhaust gas through the cascade, wherein the method comprises thesteps of:providing a first flow regulating vane adjacent one end vane ofthe cascade vanes, providing a second flow regulating vane adjacent another end vane of the cascade vanes, pivoting the first flow regulatingvane about an axis parallel with the one end vane pivot axis, said firstflow vane being pivoted oppositely with respect to the cascade vanesover the thrust vectoring range of motion and in unison with respect tothe cascade vanes over the stowing range of motion, and pivoting thesecond flow regulating vane in unison with the first flow regulatingvane over the thrust vectoring and stowing ranges of motion.